#include<stdio.h>
int IsAllDigit(char p[]);
int main()
{	    	   	
    char a[80];
    printf("Please input a string:\n");
    gets(a);
    if (IsAllDigit(a))
        printf("The string is a digit string.");
    else
        printf("The string is not a digit string.");
}	    	   	

int IsAllDigit(char p[])
{	    	   	
    int flag = 1, i;
    for (i = 0; p[i] != '\0'; i++)
    {	    	   	
        if (p[i] < '0' || p[i] > '9')
        {	    	   	
            flag = 0;
            break;
        }
    }
    return flag;
}	    	